A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Bacteria that live in the intestines need para-aminobenzoic acid to survive. Para-aminobenzoic acid is found in grains and foods from animals. It is being studied as a radiosensitizer (a substance that makes tumor cells more sensitive to radiation therapy) and in the treatment of certain skin disorders. Also called aminobenzoic acid and PABA.